Patent GB-807389-A (GB)
Title: Improvements in or relating to telephone instruments of the standing hand set type
IPC: H04M1/02
Filed: 1957-02-20
Abstract: 807,389. Sets. TELEFONAKTIEBOLAGET L. M. ERICSSON. Feb. 20, 1957 [Feb. 21, 1956], No. 5761/57. Class 40 (4). A telephone handset of the kind which can stand on a supporting surface and has cradle switch contacts operated by a plunger which in one position protrudes from the handset and in a second position is pressed inwardly by the supporting surface to lie flush therewith, is characterized in that the plunger is latched in its second position, the latch being manually released by pressing the plunger into the handset. In Fig. 1 the plunger 3 is shown slidable in a bearing on a base 2 of a handset 1 and has a cylindrical head 6 with a projecting rim 7 capped by a nose 8. With a button head 9 of the plunger resting on a supporting surface 20 the rim 7 lodges on the upper edges of opposed spring arms 5 to latch the plunger. If the head 9 is pushed inwardly the nose 8 deflects a spring blade 11 limited downwardly by an arm 12 and when the head 9 is released the plunger is thrown with sufficient momentum to drive the rim 7 through the springs 5 which close over the nose 8 and operate cradle switch contacts. When the handset is replaced on a supporting surface the nose 8 separates the springs 5 and relatches the plunger on the rim 7. An alternative, using the same method of ejection, is shown in Fig. 6 where a notch 15 in the head 6 is engaged by springs 5 having V-shaped pawls, or, as shown in Fig. 9, the plunger may carry a spring 16 with a projection 17 engaging a notch on a supporting part of the instrument. In the embodiment shown in Fig. 10 the plunger 3 has a reduced portion 3a at its upper end to which a slide block 8 is secured. Guide portions 11 on the block 8 engage vertical slots in pillars 13 mounted on a bridge 14. The block 18 slides up and down with the plunger 3 and carries a projecting cam 16 co-operating with a pin 7 mounted on a spring-blade 6 for transverse movement across the path of the cam; seen best in Figs. 15, 15B and 15C. When the plunger lies with its button head 9 flush with a supporting surface, the pin 7 lies beneath a lip 16c of the profile of cam 16, thus latching the plunger against movement outwardly of the instrument, Fig. 15. When pushed inwardly the cam 16 forces pin 7 sideways to the right until it rounds the bottom of the cam and springs back to lie under the cam surface 16a, Fig. 15B. When the plunger is allowed to return downwards the pin 7 is forced to the left until it flies free to strike a stop 21 and lie above cam surface 16b. The plunger is now at its lowermost point and the cradle switch contacts are made. When the instrument is replaced on a supporting surface the pin 7 is forced to the right until it lodges under the lip 16c to re-latch the plunger. The cam carrying block 8 may be held stationary while the pin 7 is mounted on the plunger and moved up and down. Figs. 17 to 20, not shown, illustrate the invention as incorporated in a handset having a dialling mechanism, the plunger passing through a bore in the finger-plate shaft. Specifications 612,005 and 698,927 are referred to.